code: def test_directed():
      """
      A directed graph with no bi-directional edges should yield different a graph hash
      to the same graph taken as undirected if there are no hash collisions.
      """
      r = 10
      for i in range(r):
          G_directed = nx.gn_graph(10 + r, seed=100 + i)
          G_undirected = nx.to_undirected(G_directed)
  
          h_directed = nx.weisfeiler_lehman_graph_hash(G_directed)
          h_undirected = nx.weisfeiler_lehman_graph_hash(G_undirected)
  
          assert h_directed != h_undirected
  
imports: import pytest
  import networkx
  from networkx.generators import directed
label_desc: Use image node_id 2 for calling a global function with example usage: test_directed() without return types